This invention relates to electric motors and in particular, to a miniature electric motor having an internal cooling fan.
Miniature electric motors with internal cooling fans are well known with the fan providing a source of cooling air flow through the motor so that the motor can run at a higher current rating or power than it could be otherwise.
In a miniature electric motor, and in particular, miniature PMDC motors with wound rotors, the fans are attached directly to the armature core, as shown in GB 2189944 for example or they may be mounted directly onto the commutator about the terminals or tangs. Commutator mounted fans are made of more expensive thermoset plastic to withstand the high temperatures of the commutator which can be especially high under stall conditions when the rotor is locked, resulting in no cooling air flow from the fan.
The armature core fan can be made of cheaper thermoplastic as it is not in direct contact with the commutator and thus, does not have to withstand such high temperatures.
In a PMDC motor with a wound rotor in which the rotor windings are connected to the commutator by way of Insulation Displacing Terminals (IDT) as shown for example, in GB 2128818, lead wires are strung across recesses in a crown or terminal portion of a base of the commutator into which at least the terminals of the commutator segments are inserted. The terminal portion, however, provides a big impediment to cooling air flow across the commutator surface generated by a fan fixed to the rotor core due to the physical size and location of the terminal portion.
Thus, there is a need for an internal cooling fan arrangement within a miniature electric motor having a commutator with insulation displacing terminals which has or can readily receive/support an internal cooling fan for the motor.